16 
N . C. Experiment Station 
6. The fungus may be said to possess in its life cycle three stages, a 
vegetative or mycelial stage, a sclerotial stage, and an apothecial or 
ascogenous stage. 
7. A study has been made of the development of S. trifoliorum from 
diseased crimson clover in comparison with S. libertiana from lettuce 
affected with drop. The two differ in luxuriance of mycelial growth, size 
of hvphae, size of sclerotia, and size of asci and ascospores. 
8. In the infection experiments S. trifoliorum has been successfully 
inoculated into lettuce and crimson clover and S. libertiana into lettuce, 
crimson clover, and vetch. 
9. The comparative morphological studies indicate that S. trifoliorum 
and S. libertiana are distinct species. Furthermore, the reciprocal inocu 7 
lations clarify existing accounts of the identity and relationship of the 
two organisms. 
10. The feature of most economic importance in the life history of the 
stem rot fungus is that the sclerotia may be mixed with the seed at time 
of harvest. The planting of such contaminated seed then insures the 
spread of the disease to new localities. Other agencies as implements, 
soil, and hay from infected fields may serve as a means of spread. 
11. The sclerotia which remain dormant in infested soils constitute the 
means of keeping the organism alive where the disease has once appeared. 
Burial by deep plowing prevents their germination and thus prevents the 
spread of stem rot. Many sclerotia decay from natural causes and many 
are destroyed by insects. 
12. Introduction of the disease into fields where it is not yet present 
should be prevented by avoidance of contaminated seed, by the exercise 
of care when soil is used to inoculate new fields with the legume nodule 
forming bacteria, and by not returning manure to clover fields when hay 
from infested fields has been fed. 
13. The adoption of a system of crop rotation is the only reliable 
means of control for infested fields. Cowpeas and soybeans can be used 
in this rotation system to increase and maintain soil fertility, and winter 
oats and rye can serve as cover crops. 
